What is the definition of 'chemical weapon'?

‘Chemical weapon’ has become the general term for what used to be called poison gas. There are other chemical weapons, like phosphorous shells and tear gas, that were used in WW2. In fact all active ordnance, from artillery shells to cruise missiles, is chemical.

Since the term ‘Chemical Weapon’ has now entered the realm of foreign policy, as a line that cannot be crossed, is there an official definition?




The Chemical Weapons Convention defines them thus;

Going back a bit the Geneva Protocol bans “…the use in war of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices”


Thanks for the link.
So, phosphorous is incendiary and toxic, it qualifies as a chemical weapon used by the US in WW2.


Phosphorus does not qualify as a chemical weapon. It is toxic, but that’s not why it’s used: It’s used because it’s incendiary. Under the definitions given, it’s “except where intended for purposes not prohibited under this Convention”: Its intended purpose is to burn, and burning is not prohibited.

One assumes that Napalm is similarly not considered a chemical weapon. I had never really thought about that before. Given the prime purpose of mustard gas and its ilk were as blistering agents a chemical agent with a prime purpose of burning skin would seem a very fine distinction.

It is not prohibited for its typical uses, including as a battlefield obscurant, but it is a controversial legal matter if it is prohibited to use as a toxic gas to attack personnel. There does not appear to be a consensus as to whether such a use is prohibited or not.

The US “tunnel rats” used phosphorus based weapons in Vietnam. The irritating/toxic smoke was the desired effect.

In fact the US Army in World War 2 did have a “Chemical Corps” for their artillery they deployed into combat. However their specialty was smoke and phosphorous rounds so it was more concealment than actual offensive chemical weapons use.

Well that and the fact that we were fighting the biggest producer and user of chemical weapons in the previous war. There was always the possibility that the Nazis would get desparate enough to use them again. Just like why we have maintained a chemical Branch in all the decades since.